1. The Technical Field
The present invention relates to a control panel interface for applications using touch sensors as control input and output devices. More particularly, it relates to a control panel having a touch sensor and integrated decoration.
2. The Prior Art
Known touch sensors typically include a touch pad having one or more electrodes and an associated circuit that induces an electric field about the touch pad and responds to changes to the electric field when the electric field is disturbed by a stimulus such as a user's touch or proximity. The touch pad and associated circuit are typically disposed on a substrate such as a printed circuit board or glass panel. This touch sensor subassembly is then attached to a second substrate, typically a nonconductive panel made of glass or plastic, that forms the face of a control panel, which presents itself to the user of the controlled device and a portion of which (the “touch surface”) a user touches or approaches to disturb the induced electric field and thus trigger the touch sensor. This second substrate typically includes a decorative layer disposed thereon. This decorative layer can serve to make the touch sensor more ergonomic, for instance, by alerting the user to the presence and location of an underlying touch pad, by informing the user of the response a particular touch pad will effect when triggered or by otherwise creating an easily managed human interface.
These known touch sensor assemblies protect the touch pad and associated circuitry from environmental conditions that exist at the touch surface while providing an aesthetic or ergonomic face. However, this design involves separating the touch sensor's touch surface from the corresponding touch pad and thus adds thickness to the touch sensor assembly as a whole. The associated separation of the touch surface from the touch pads of the sensor attenuates the strength of the electric field proximate the touch surface, and the increased thickness of the touch sensor prevents the touch sensor from being used in certain applications requiring particular flexibility or thinness. Also, the use of a second substrate increases the cost and complexity of the touch sensor assembly process. Further, these known touch sensors limit the integration of back-lighting, indicators and displays. When these features are included, they typically are located adjacent to the touch sensor or, alternatively, apertures must be created in the touch sensor electrodes to accommodate them.